In A.D. 185, Chinese records note the appearance of a “guest star” that then faded away over the span of several months. In 1572, astronomer Tycho Brahe and many others watched as a previously unknown star in the constellation Cassiopeia blasted out gobs of light and then eventually disappeared. And 30 years ago, the world witnessed a similar blaze of light from a small galaxy that orbits the...

Almost every night that the constellation Orion is visible, physicist Mark Vagins steps outside to peer at a reddish star at the right shoulder of the mythical figure. “You can see the color of Betelgeuse with the naked eye. It’s very striking, this red, red star,” he says. “It may not be in my lifetime, but one of these days, that star is going to explode.”

Ian Shelton was alone at a telescope in the remote Atacama Desert of Chile. After three hours getting a picture of the Large Magellanic Cloud, a wispy galaxy that orbits the Milky Way, he was plunged into darkness. High winds had taken hold of the rolltop door in the observatory’s roof, slamming it shut.

Thirteen years ago, astronomers witnessed the brightest stellar explosion seen from Earth since the invention of the telescope. A supernova—the violent death of a massive star—had erupted in the Large Magellanic Cloud galaxy, only 160,000 light-years away. Because of the galaxy's proximity, scientists have had a field day tracking the unfolding saga of supernova 1987A.

Thirteen years ago, astronomers witnessed the brightest stellar explosion seen from Earth since 1604. Now, they're seeing fireworks generated as material from that explosion rams into and heats up a ring of gas surrounding the exploding star.

The spectacle, 169,000 light-years away in a galaxy called the Large Magellanic Cloud, may shed light on the nature of the original...